1. Field of Invention
This invention relates to switches for use with electronic equipment, particularly to such switches and associated electronic circuitry which interfaces with, reads, and interprets the switches' settings.
2. Description Of Prior Art
Electronic engineers commonly provide DIP (Dual-Inline Package) switches for use in electronic circuits to provide a way to select various system configuration choices. DIP switches are small rectangular electronic components, usually packaged in a plastic housing having typical dimensions, in millimeters, of 6.8 to 50.8 long, 3.68 to 15.24 wide, and 2.54 to 12.7 high. The housing contains the electrical and mechanical components of the switch and a means to connect and solder the package to a mounting surface, described later. Although the acronym "DIP" is commonly used to refer to dual-inline packages, it has also been used to refer to any packaged electronic device that can plug into or be soldered to a circuit board.
There are many different kinds of DIP switches These include SPST (single-pole, single-throw), MPST (multiple-pole, single-throw), MTSP (multiple-throw, single-pole), rotary contacting, and variations of all these. A DIP switch housing can contain one or more individual switches of the above types.
The SPST DIP switch, a very common type, contains one or more SPST switches in a single package. A SPST switch consists of a single set of electrical contacts which can only move and operate in a single on or off manner When in the on position, the SPST switch is considered "closed", "transmissive" or "conductive" and provides an electrical path between a single pair of contacts. When in an off position, the electrical connection is considered "open", "non-transmissive" or "non-conductive" and thus provides essentially an infinite resistance between the contacts. Each switch has an on and off setting which is independent of the other switches in the DIP package. The package also contains a plurality of thin metal leads projecting therefrom. These leads provide a electrical path from the switch contacts to external components in an electrical system, as described later.
Other types of DIP switches have different arrangements of switch contacts which can cause the switch to operate several contacts or poles with a single throw or to allow multiple positioning of a single pole. Rotary contacting DIP switches are yet another type which use multiple electrical switch contacts to provide a selection of switching combinations in a single package.
DIP switches are used in a wide variety of applications, particularly in applications having to do with computers or microprocessor-based equipment and systems. A microprocessor is a computer built into a integrated circuit. Some examples include computer I/O (input/output) circuits, memory and video boards, communication terminals, computer printers, garage-door openers, wireless telephones, and a large number of other products
DIP switches are frequently used in computer systems to assign an address on the computer system's bus to an I/O, memory, or other option board. Address assignment refers to a function which occurs in most computer and microprocessor systems which allows the CPU (central processing unit) to select a device within the computer system with which it will transfer and receive data.
DIP switches are also used to select a security code in garage-door openers, wireless telephones, and similar devices. The DIP switch provides a simple way for a user to change a value or select a number associated with the operation of that product. These products are typically based on a microprocessor and presently require several additional components, as described below, to read the DIP switches' setting and adjust its operation accordingly.
Communications terminals are the hardware and cabling system associated with a data transmission system used with computers and other devices as a means of allowing data transfers to and from other computers, peripheral devices, and other products. Typical terminals which use DIP switches include computer printers, terminals, and monitors.
These are but a few of the more common applications of DIP switches. There are many other applications and products which use DIP switches, but these are far too numerous to list here
These applications can offer a range of data transfer options. It is highly desirable to be able to easily change the configuration or protocol of the communications signals recognized by these products. A DIP switch is frequently used to allow a user to select these various configuration options. However in order to read the DIP switches' setting, these systems must presently include several additional components to interface to the DIP switch and which add to the size, cost, and complexity of the product.
These additional and external components are required in order for the DIP switch to be used by most microprocessors, computers, or electronic circuits. Specifically, in order for the DIP switch to be read and interpreted by any system or circuit, it must have a series of pull-up or pull-down resistors, a tri-statable interface buffer, decode logic circuitry, and other devices that are in addition to and are external to the DIP switch, as described later.
These extra components usually take up at least as much room on the system circuit board as the DIP switch package itself, and can take considerable time and expense to install, assemble, and test in the electronic system where they are used. Circuit board space and the number of components in an electronic system have a direct effect on the cost of raw materials and labor to manufacture that system. Circuit design and manufacturing engineers go to extreme lengths to reduce these by whatever means are available. It would be a great advantage if it were not necessary to connect such additional devices to a DIP switch in order to use the DIP switch in an electronic system.
Several DIP switch patents, such as U.S. Pat. No. 4,376,234, entitled "DIP Switch", granted Mar. 8, 1983, to James P. Liataud, and U.S. Pat. No. 4,658,101, entitled "Sliding Type DIP Switch" granted Apr. 14, 1987 to Takashi Akimoto, Akio Kai, Massao Kobayashi, and Haruo Itoh, describe mechanical or basic electrical features of a on/off multi-pole (multiple connection) contacting switch. Others, such as U.S. Pat. No. 4,454,391 entitled "Low Profile DIP Switch" granted June 12, 1984 to Billy E. Olsson, describe a unique profile or package design. U.S. Pat. No. 4,642,734, entitled "Integrated Circuit Chip DIP Switch", granted Feb. 10, 1987 to James R. Anderson, describes an interlocking and disconnectable system for mounting a DIP switch on a disconnectable handle. U.S. Pat. No. 4,788,393, entitled "DIP Rotary Code Switch", granted Nov. 29, 1988 to Masayuki Muramatsu and Atsuo Yamazaki, describes a rotary contacting, encoded DIP switch. Rotary coded DIP switches are frequently available in decimal, binary, or hexadecimal number formats and output codes.
In all of the above DIP switches, none include the required active electronic components for using the DIP switch as part of the DIP switch assembly. Therefore these extra components must be connected externally to the DIP switch. These take up valuable circuit board space and require many interconnections on the system's circuit board. They also require extra assembly time to install and test on such circuit board. Overall product sizing and cost of a system using a DIP switch are directly and substantially increased by these factors.
I believe that DIP switch designers and manufacturers have not provided an improved design because they are mechanically oriented and are mostly concerned with the mechanical operation and packaging of the DIP switch. Similarly electronic engineers do not generally have a background or interest in pursuing mechanical solutions to their engineering problems.